Field of the Invention
The present invention relates to an electric power supply system.
Discussion of the Background
In a Japanese Patent Application Laid-Open Publication No. 2013-059161, the problem to be solved is to provide an electric motorcar which has a high output density battery and a high energy density battery and which is capable of delaying the deterioration of the high energy density battery even in such a condition where the high energy density battery does not have many opportunities to be used for travelling (abstract, [0006]).
In order to solve the problem the electric motor vehicle 100 of the Japanese Patent Application Laid-Open Publication No. 2013-059161 (abstract) is provided with a first battery (high output density battery) 12 which can be charged from an external power source, and a second battery (high energy density battery) 22, and a controller 8 for controlling a charge of electricity to the batteries 12, 22. The controller 8 executes a power transfer step, a first battery charging step and a second battery charging step. In the power transfer step, the first battery 12 is charged by using the second battery 22 prior to the power charge by using the external power source. In the first battery charging step, the first battery 12 is charged by using the external power source. In the second battery charging step, the second battery 22 is charged by using the external power source. The deterioration of the second battery 22 is delayed by lowering SOC of the second battery 22 during charging process.